Antireverse trigger for an ignition system

ABSTRACT

In an electrically triggered ignition system for two-cycle internal combustion engines, utilizing a trigger coil in which a trigger signal is produced by a flux-varying member carried by a rotating part of the engine, a second flux-varying member is provided on such rotating part which during reverse motion of the engine produces a trigger signal in the trigger coil which is so timed relative to the engine cycle that reverse engine operation cannot be sustained.

l United States Patent PATENTEU JAN 1 2 191| INVENT BOB O. BU N ATTORNEYS PMENTEDJAMZIQ?! SI-554,179

SHEET 2 UF a HIGH SPEED TRIGGERING FORWARD ROTATION LOW SPEED TRIGGERING FORWARD ROTATIYON INVENTOR BOB O. BURSON 22M/ww 5W 'ATTORNEYS PATENTEU JAM 2 |97| SHEET 3 F 4 LOW SPEED TRIGGERING REVERSE ROTATION LOW FORWARD SPEED 60 TRIGGERING LOW REVERSE SPEED TRIGGERING INVENTOR BOBv O. BURSON ATTORNEYS PATENTEUJANlzmn .3D-554,179

y SHEET u of 4 FIG. 8

INVEN BOB O. BU N aM/Maw ATTORNEYS ANTIREVERSE TRIGGER FOR AN IGNITION SYSTEM BACKGROUND OF THE INVENTION This invention relates to ignition systems for two-cycle internal combustion engines, and deals morel particularly with such a system which eliminates any possibility of the associated engine operating in the reverse direction.

The basic principals of this invention may be applied to various types of two-cycle internal combustion engines both of large and small size and of one or more cylinders. The invention is, however, particularly well adapted for use with relatively small single cylinder engines ofthe type commonly used for powering lawnmowers, chain saws and other similar tools, and it is disclosed herein by way of example in association with such an engine. In recent years, various different electrically .triggered ignition systems have been proposed and used with such engines to replace the previously more conventional mechanical breaker system. One general type of such ignition system is commonly referred to as a condenser discharge system and utilizes a condenser which is, during each cycle of the engine, charged by an associated generating means and later discharged through a step-up transformer to produce firing of the spark plug, the discharge being controlled by a trigger signal supplied by a trigger coil in which a trigger signal is induced by a flux-varying element carried by a rotating part of the engine. In two-cycle engines equipped with a capacitor discharge-type ignition system, or other type of electrically triggered ignition system, it has sometimes been possible, during the starting of the engine, for theengine to accidentally move and start in the reverse direction and for such reverse operation to be sustained. This reverseoperation may, in turn, cause damage to the tool powered by the engine and/or may present a dangerous situation with regard to the person using the tool.

The object of this invention is, therefore, to provide a means for positively eliminating the possibility of such accidental reverse operation.

SUMMARY OF THE INVENTION This invention resides in an electrically triggered ignition system utilizing a triggering coil for producing trigger signals which control the timing of the firing of the associated spark plug. The trigger signals are induced in the trigger coil by a flux-varying member which is mounted on a rotating part driven in synchronism with the engineoperation and located so as to cause the firing to occur at a proper time throughout each engine cycle during operation of the engine in the forward direction. Additionally, the system includes a second flux-varying member also carried bysuch rotating part of the engine for cooperation with the trigger coil. This second fluxvarying member is so located that during forward operation of the engine the trigger signals induced thereby in the trigger coil occur when no energy is available for causing firing of the spark plug so that such signals therefore have no effect on the normal operation of the engine. The location of this second flux-varying member is, however, such that during any accidental reverse operation of the engine, as may occur during starting, a trigger signal is produced which is so timed relative to the engine cycle that further engine operation cannot be sustained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a vertical sectional view taken through the flywheel of an engine equipped with an ignition system embodying this invention, the flywheel comprising part of said ignition system.

FIG.,2 is a vertical sectional view taken on the line 2-2 of FIG. l.

FIG 3 is a schematic wiring diagram showing the electrical components used in the ignition system of FIG. l.

FIG. 4 is a schematic view showing the positions of the trigger stator and that two pole shoes of the flywheel at the instant triggering occurs during forward high-speed operation of the associated engine.

FIG. 5 is a view similar to FIG. 4 but shows the relative positions of the parts occupied at the instant of triggering during low-speed forward operation of the associated engine.

FIG. 6 is a view similar to FIG. 4 but shows the relative positions of the parts occupied at the instant of triggering during low-speed operation ofthe engine in the reverse direction.

FIG. 7 is a schematic diagram illustrating the various points at which triggering occurs relative to the engine cycle. l

FIG. 8 is a fragmentary vertical sectional view similar to FIG. l, but showing an alternative form of flywheel which may be used in place of that shown in FIG. 1.

FIG. 9 is a perspective view showing the pole shoe insert used in the flywheel of FIG. 8.

FIG. 10 is an enlarged vertical sectional view taken on the line 10-10 ofFlG. 8.

FIG. 1l is an enlarged sectional view taken on the line 11-11 of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning to the drawings, and first considering FIGS. l, 2, and 3, these figures illustrate an electrically triggered ignitiofn system embodying this invention and for use with a two-cycle single cylinder internal combustion engine. Except for the addition of a second flux-varying member to produce an antireverse trigger signal in the trigger coil, the illustrated system is generally similar to that shown in copending patent application Ser. No. 758,563, tiled Sept. v9, 1968 entitled Breakerless Ignition System With Separate Triggering Magnet, to which reference may be made for additional understanding of its construction and operation. This system is a capacitor discharge system wherein a capacitor is charged and discharged during each operating cycle of the engine to produce the spark at the spark plug, but it should be understood that this ignition system has been chosen by way. of example only and that the antireverse feature, which is the basis of this invention, may at least in its broader aspects be applied as well to other triggered ignition systems for twocycle engines.

FIGS. 1 and 2 show the mechanical parts of the ignition system, and referring to these figures, the reference numeral 10 indicates a flywheel type rotor which is attached to the crankshaft l2 of the associated engine 13 so as to be rotated in synchronism with the operation of the engine. Embedded in the rim of the rotor 10 is a main magnet assembly 15 comprising a permanent magnet 14 and two pole pieces 16, 16 providing spaced-apart pole faces 18, 18 of opposite magnetic polarity on the outer circumferential surface of the rotor. A stator core 20 having two legs 22, 22 is positioned adjacent the rotor l0 and carries a generating coil 24 on one of its legs. Therefore, during each revolution of the rotor l0 the magnet assembly 15 passes the two legs of the stator 20 and produces a varying magnetic flux through the stator'core which, in turn, induces a voltage in the generating coil 24. This voltage is used to provide the power for firing the associated spark plug as hereinafter described.

The timing of the firing of the spark plug in the ignition system of FIGS. 1 to 3 is controlled by a trigger coil 26 which also cooperates with the rotor 10 and has a triggering signal induced therein during each revolution of the rotor. The trigger coil 26 is mounted on one of the legs of a two-legged stator 28 located inside the rim of the rotor, the stator 28 consisting of a permanent magnet 30 and two legs 32 and 33 of magnetic material. The two legs 32 and 33 extend outwardly toward the rim of the rotor and have end faces which cooperate with a flux-varying member or pole piece 34 embedded in the rotor rim and having a pole face 36 of a circumferential length approximately equal to the maximum spacing between the end edges of the pole faces of the stator legs 32 and 33. Accordingly, during each revolution of the rotor 10, the pole piece 34 passes the trigger stator 28 and induces a varying flux therein which generates a trigger signal in the triggering coil v 26 used to control the timing of the ,firing of the spark plug.

As indicated by the arrows in FIG. l, the illustrated rotor l rotates in the clockwise direction, as viewed in FIG. 1, during normal forward operation of the engine and the relative locations of the main generating means and trigger signal-generating means are such that the signal produced by the main generating means to power the firing of the spark plug is generated in advance of the trigger signal used to control the timing of the firing. More particularly, FIG. 1 shows the rotor at the position occupied when the main power signal generated in the generating coil 24 is at approximately the midpoint of its waveform, the first half of which is used to power the spark at the spark plug as hereinafter described, the main magnet assembly being aligned with the stator 20. At this position of the rotor, the trigger pole piece 34 is spaced a significant angular distance from the trigger stator and does not produce a trigger signal in the trigger coil 26 until well after the part of the waveform generated in the generating coil 24 which is used to power the spark is fully completed.

The electrical circuit and components of the ignition system, the mechanical aspects which are shown in FIGS. 1 and 2, is shown in FIG. 3. Referring to this figure, the main generating coil 24 is connected across a condenser 38 through a diode 40 with another diode 42 being connected in parallel therewith, the two diodes 40 and 42 being poled so that the condenser 38 is charged only when the voltage induced in the generating coil 24 is of one polarity. That is, as the magnet assembly l5 passes the stator 20, a voltage waveform is induced in the generating coil 24 which is first of one polarity and then of the opposite polarity, and only that portion of the wave which is of one polarity is used to charge the condenser 38. 4

The condenser 38 is also connected across the primary coil 44 of a step-up transformer 46 having a secondary 48 connected to the spark plug 50. In the circuit between the condenser 38 and the primary winding 44, is a silicon-controlled rectifier 52 having its anode and cathode terminals connected in series with the condenser and the primary winding. The trigger coil 26 is connected between the gate terminal and the cathode terminal of the silicon-controlled rectifier 52 and through the trigger signal induced therein controls the conduction of the silicon-controlled rectifier so as to time the discharge of the condenser 38 through the primary winding 44, and thereby timing the firing of the spark plug 50.

In the normal operation of the systemshown in FIG. 1 to 3, with the engine and rotor moving in the forward direction, the magnet assembly 15 first passes the stator 20 and induces a voltage in the generating winding 24 which charges the condenser 38. Some time after this charging, the trigger pole piece 34 passes the legs 32 and 33 of .the trigger stator 28 and induces a trigger signal in the trigger coil 26 which switches the silicon-controlled controlled rectifier to a conducting state, thereby discharging the condenser 38 through the primary winding 44 of the step-up transformer and inducing a high potential in the secondary winding 48 to cause the occurence of a spark at the spark plug 50. As the pole piece 34 moves away from the trigger stator, a reverse voltage induced in the trigger coil 26 and a reverse voltage is applied across the anode and cathode terminals of the silicon-controlled rectifier, as a result of resonance between the condenser 38 and winding 44, to positively switch the silicon-controlled rectifier to a nonconducting state, thereby conditioning it for operation on the following cycle.

As explained in more detail in the aforementioned copending application Ser. No. 758,563, the illustrated construction of the trigger signal-producing means is such that an automatic spark advance is achieved whereby the timing of the occurence of the spark is advanced in response to increases in the engine speed. That is, during low-speed operation of the engine, triggering occurs near the point at which the pole piece 34 approaches the trailing stator leg 33 and during highspeed operation, triggering occurs at the point at which the pole piece 34 approaches the leading pole stator leg 32, the firing occuring at intermediate points for intermediate speeds.

As so far described, the ignition system of FIGS. l to 3 is similar to that shown and described in copending application Ser. No. 758,563. In accordance with this invention, however, the system further includes a means for preventing operation of the engine in the reverse direction in the event the engine is for some accidental or inadvertent reason started in motion in the reverse direction. Referring to FIG. 1, this means takes the form of a second flux-varying member or pole piece 54 embedded in the rim of the rotor 10 for cooperation with the trigger stator 28. The second pole piece 54 is identical to the first pole piece 34 and is so located relative to other parts of the system as not to interfere with the normal operation of the engine in the forward direction and so as, during motion of the engine in the reverse direction, to induce a triggering signal in the trigger coil 26 which occurs at such a time in the engine cycle that the accompanying firing of the spark plug will not sustain further reverse engine operation.

Referring again to FIG. 1, and considering first the effect of the second pole piece 54, during normal forward operation of the engine, it will be noted that during each revolution of the rotor 10 of the main magnet assembly 15 first passes the stator 20 and produces a signal in the generating coil 24 which charges the capacitor 38. Thereafter, the first pole piece 34 passes the trigger stator 28 and induces a trigger signal in the trigger coil 26 which fires the spark plug 50 by switching the silicon-controlled rectifier 52 to a conducting state. This firing of the spark plug drains the charge from the capacitor 38. Thereafter, the second pole piece 54 passes the trigger stator 28 and induces another trigger signal in the trigger coil 26.

At this time, however, due to the drained or discharged condition of the capacitor 38, the trigger signal has no effect and no additional spark is produced at the spark plug.

Considering next the operation of the system of FIGS. 1, 2 and 3 during accidental reverse motion of the rotor 10, this motion being in the counterclockwise direction as viewed in FIG. 1, it will be understood that the main magnet'assembly 15 first passes the stator 20 and induces a voltage signal in the generating coil 24 which charges the capacitor 38. As the rotor thereafter rotates further inthe reverse direction, the second pole piece 54 first passes the trigger stator 28 before the pole piece 34 and induces a trigger signal in the trigger coil 26 which switches the silicon-controlled rectifier 52 to its conducting state and discharges the condenser 38 through the primary winding 34 causing firing of the spark plug 50. As explained in more detail hereinafter, this firing of the spark plug is so timed as to occur at a point in the engine cycle that it will not sustain further reverse operation. As the rotor 10 moves further in the reverse direction, the'pole piece 34 next passes the trigger stator 28, but due to the now-discharged condition of the capacitor 38, the signal induced thereby in the trigger coil 26 will not cause firing of the spark plug.

FIGS. 4, 5, 6 and 7 show in more detail the relative angular spacings and dimensions of the various parts of the trigger means and the points at which the spark plug is fired relative to the engine cycle for different speeds and directions of rotation of the rotor l0.

Considering first FIG. 4, this FIG. shows the relative positions of the trigger stator 28 and the two trigger pole pieces 34 and 54 at the positions occupied at the instant of firing during high-speed operation of the associated engine in the forward direction. More particularly, during high-speed forward motion of the rotor, firing of the spark plug S0 occurs at approximately the illustrated position of FIG. 4 at which the leading edge 56 of the trigger pole piece 34 begins to overlap the leading edge 58 of the leading stator leg 32. In FIG. 4, the line 60 indicates the position of the leading edge 56 of the pole piece 34 when the associated engine 13 is in its top dead center position. Therefore, from FIG. 4, it will be noted that during highspeed forward rotation of the rotor, firing of the spark plug occurs 30 before top .dead center. This angular position at which firing occurs during high-speed operation may be varied depending on the design of the associated engine with which the ignition system is used, and this particular angular position for high-speed firing, as well as the other angular relationships shown in FIGS. 1 to 7 have been chosen by way of example only. In the example presented, however, it should be noted that each of the pole faces of the legs 32 and 33 of the stator 28 have an angular extent of 7 and are separated from one another by a 13 gap so as to produce a 27 spacing between the leading edge 58 of the leading leg 32 and the trailing edge 62 of the trailing leg 33. The two pole pieces 34 and 54 each have pole faces of approximately 27 circumferential extent, and the spacing between the leading edge 56 of the pole piece 34 and the trailing edge 64 of the pole piece 54 is 122.

Considering next FIG. 5, this figure shows the relative positions of the trigger stator 28 and the pole pieces 34 and 54 at the instant of firing during low-speed forward operation of the engine. More particularly, during such low-speed forward operation, the firing of the spark plug 50 occurs at the rotor position illustrated in FIG. 5 whereat the leading edge 56 of the trigger pole piece 34 starts to overlap the leading edge 66 of the trailing trigger stator leg 33. As illustrated in FIG. 5, this firing therefore occurs when the associated engine is from its top dead center position.

Referring next to FIG. 7, this figure shows schematically the cycle of the associated engine 14, at least as regards the timing of the opening and closing of its exhaust and intake valves and 'the timing of the firing of the spark plug relative to such cycle. In this figure, the line 60 indicates the top dead center position of the engine and the line 69 the bottom dead center position of the engine. The band 70 indicates the condition of the intake valve during a full cycle of operation and the band 72 likewise indicates the condition of the exhaust valve during a full cycle of operation. ln each of the bands 70 and 72, the crosshatched portion indicates the period during which the associated valve is closed and the noncrosshatched portion indicates the period during which the associated valve is open. Therefore, considering the intake valve as represented by the band 70, it will be understood that' the intake valve is closed from the top dead center position until reaching a point l 10 beyond top dead center and is then opened and remains open until again reaching a point spaced` 110 in advance of top dead center at which point it is again closed. Likewise, in moving from top dead center the exhaust valve remains closed until reaching a point spaced 95 beyond top dead center and then opens, and it remains open until reaching a point spaced 95 in advance of top dead center at which point it is again closed.

In FIG. 7, the line 74 indicates the point at which firing of the spark plug occurs during low forward speed operation, such point being spaced 10 in advance of the top dead center position in accordance with FIG. 5. The line 76 represents the point at which tiring occurs during high forward speed operation, such point being spaced at 30 in advance of the top dead center position in accordance with FIG. 4.

lf the rotor l0 is moved in the reverse direction, and does not include the second pole piece 54, a trigger signal will be induced in the trigger coil which occurs some time after the top dead center position, and although this timing is not proper for good engine operation, it may be sufficient to sustain the engine in operation. Therefore, to prevent this possibility, the second pole piece 54 is so located that during reverse operation, the trigger signal generated thereby occurs before that of the pole piece 34 and at ta time in the engine cycle at which it cannot sustain operation.

Referring to FIG. 7 and considering the engine to be now moving in the reverse or counterclockwise direction, most two-cycle engines will not operate if the timing of the firing occurs more than approximately 40 before the top dead center position, the line 78 in FIG. 7 representing such 40 position. Therefore, in accordance with this invention, the second pole piece 54 is so located that during reverse rotation, and at the low cranking speeds which are involved, it causes the production of a trigger signal which occurs well in advance of the 40 before top dead center position represented by the line 78. Any timing of the spark to occur in advance of the 40 before top dead center position (and of course well beyond the top dead center position) will be sufficient to prevent continuance of engine operation in the reverse direction and, therefore, will meet the general aims of this invention. Preferably, however, the timing is further so selected that the firing occurs when the exhaust valve is open so any combustion which does occur will exhaust through the exhaust valve without producing any force on the engine piston. Although in accordance with this degree of preference the firing may occur at any point in the period during which the exhaust valve is open but the intake valve closed so that as the combustion takes place, no backfiring through the intake valve is possible. Therefore, with reference to FIG. 7, the preferred period during -which triggering occurs during reverse operation is the period occuring between the point 80, at which the intake valve closes during movement in the reverse direction toward top dead center, and the point 82, at which the exhaust valve closes during such-reverse movement toward top dead center.

The relative angular spacings of the various parts, as shown in detail in FIG. 4, achieves firing, during reverse rotation` which occurs within the desired period during which the exhaust valve is open and intake valve closed. More particularly, referring to FIG. 6, this figure shows the relative positions of the illustrated parts at the instant of firing during low-speed reverse operation of the engine. In this case` firing occurs when the now-leading edge 64 of the pole piece 54 starts to overlap the now-leading edge 84 of the now-trailing stator leg 32. At his instant, the reference edge S6 of the pole piece 34 is spaced 100 from the top dead center position as indicated by the line 60. Therefore, as shown in FIG. 7, this firing occurs at the point indicated by the line 86 in FIG. 7 which is located between the points and 82 as desired. Accordingly, from FIG. 7, it will be understood that if the engine is inadvertently started in motion in the reverse direction during starting, which involves a low speed of the engine and rotor, the second trigger pole piece 54 will cause the spark plug to be fired at the point indicated by they line 86 at which instant the exhaust valve is opened and the intake valve closed so that any cornbustion which does take place will be exhausted through the exhaust valve without powering the piston and without backfiring through the intake valve, and will therefore not add any power to the engine capable of sustaining it in such reverse motion with the result that such reverse motion will immediately cease.

In the mechanical construction of the rotor l0 shown in FIGS. l and 2, the two triggering pole pieces 34 and 54 are in the form of individual inserts of magnetic material which are embedded separately from one another in the rim ofthe rotor during the casting of the rotor, the rotor except for the various inserts embedded therein being made of aluminum or other nonmagnetic cast material. Initially, the inserts 34 and 54 extend radially inwardly toward the center of the hub beyond the positions finally occupied by their pole faces, and the pole faces are produced thereon by machining the inner surface of the rotor rim to bring them to true concentricity and to a definite fixed radial dimension This form of flux-varying insert is not, however, essential to the broader aspects of the invention and, if desired, the two flux-varying members used with the trigger stator may take various different forms other than that of the inserts 34 and 54.

FIGS. 8 to l1, for example, show one other form of fluxvarying member for the trigger stator. In these figures, the rotor is indicated at 90 and is or may be identical to the rotor l0 of FIGS. 1 and 2 except for including the different form of trigger flux-varying member. More particularly, in the rotor 90 the two flux-varying members 92 and 94, corresponding respectively to the members 34 and 54 of FIG. I, are part of a single insert 96 shown by itself in FIG. 9. The members 92 and 94 are similar to the members 34 and 54 of FIG. I except that they are joined by an integral arcuately extending section 98 which accurately angularly locates the two members 92 and 94 relative to one another. As shown best in FIGS. l0 and Il,

the members 92 and 94 extend into the area of the web 100 of the rotor 90 so that the connecting section 98 of the insert 96 is located within the web 100 and, therefore, is in an out-ofthe-way concealed position at which it has little or no effect on the action of the two members 92 and 94 relative to the trigger stator 28.

Due to the connecting piece 98 joining the two members 92 and 94, any difficulty in accurately locating the two members angularly relative to one another during the making of the rotor 90 is eliminated, it being necessary only to properly locate the one single piece 96 prior to the molding or casting operation.

l claim:

l. ln an ignition system for a two-cycle internal combustion engine having a spark plug and a rotatable part rotated in synchronism with the operation thereof, the combination comprising a trigger coil, means connected with said trigger coil for controlling the firing of said spark plug in response to a trigger signal generated in said trigger coil, a first flux-varying member carried by said rotatable part for generating a trigger signal in said trigger coil as said rotatable part is rotated, said first flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during forward operation of said engine as to cause firing of said spark plug at such a point in the operation cycle of said engine as to sustain operation of said engine in said forward direction, and a second flux-varying member also carried by said rotatable part for generating a trigger signal in said trigger coil as said rotatable part is rotated, said second fluxvarying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during reverse operation of said engine that it causes firing of said spark plug at such a point in the operation cycle of said engine as not to sustain said reverse operation.

2. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim l further characterized by a main generating means for generating power used for firing said spark plug, said main generating means including a part also carried by said rotatable part which carries said first and second flux-varying members.

3. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim 2 further characterized by a condenser connected with said main generating means so as to be charged thereby during each revolution of said rotatable part, means connected with said condenser for producing a spark at said spark plug in response to the discharge of said condenser therethourgh, and an electronic switch device connected between said condenser and said spark-producing means and coupled with said condenser through said spark-producing means in response to the trigger signal produced by said trigger coil.

4. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by said second flux-varying member being so located on said rotatable part that the trigger signal induced therein is so timed during reverse operation of said engine as to cause firing of said spark plug at a point in the operating cycle of said engine which is more that 40 in advance of the top dead center position of such cycle.

5. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim l further characterized by said second flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during reverse operation of said engine that it causes firing of said spark plug within the period during which the exhaust valve of said engine is in an open condition.

6. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim l further characterized by said second flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during reverse operation of said enine that it causes firing of said spark cplug within the period uring which the'exhaust valve of sai engine is in an open condition and the intake valve of said engine is in a closed condition. d

7. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim l further characterized by a trigger stator comprising a permanent magnet and two stator legs on one of which stator legs said trigger coil is mounted, said trigger stator legs extending toward said rotatable part and said first and second flux-varying members being angularly spaced on said rotatable part and arranged to pass said trigger stator in sequence so as to each induce a trigger signal therein during each revolution of said rotatable part.

8. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim 7 further characterized by said rotatable part being made primarily of a nonmagnetic material and said first and second flux-varying members comprising pieces of magnetic material carried by said rotatable part.

9. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim 8 further characterized by said two pieces of magnetic material comprising said first and second flux-varying members being connected by a thin connecting section of magnetic material integral therewith which accurately angularly located said two mem- Vbers relative to one another, said connecting section being located beyond the zone of said trigger stator.

l0. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by a condenser, means for charging said condenser once during each revolution of said rotatable part, means connected with said condenser for producing a spark at said spark plug in response to the discharge of said condenser therethrough, an electronic switch device between said condenser and said spark-producing means and coupled with said trigger coil for controlling the timing of the discharge of said condenser through said spark-producing means in accordance with the occurence of the trigger signal produced by said trigger coil.

l1. ln an ignition system for a two-cycle internal combustion engine, the combination defined in claim 10 further characterized by a trigger stator located adjacent said rotatable part and carrying said trigger coil, and said two flux-varying members being angularly located on said rotatable part so as to successively pass said stator and induce successive trigger signals in said trigger coil as said rotatable part is rotated.

- gjg@ UNETED sr :ris PATENT orvcm CERTIFECATE GF' CORRECTION l' ,January 12, 1971 Patent. No. .Dated Invencor(s) Bob O. Burson It is certified that error appears in theabove-identified patentV and that said Letters Patent are hereby corrected as shown below:

C C01. 1, line 73, "that" should {read thef I' Col; 3, line 52, delete 'second occurrence of "controlled".

' Col. 3, line 57, following "voltage" insert --is. Col. 4, line 21, lfollowing ','10" delete "of". Col. 5, line 63,' "ta" should read -)a-. C01. 6, line 11, -foll'owing "open" insert --it. is

still further more strictly pre'ferredthat. .the timing be such .that the firing occur While the 'exhaust vlve is open`.

Col. 6, line 30, "his" should read -thiS-.. Col. 6, `line 58, insert a period 1 following "dimension". V

' Col- '1, line 25, "oper-ation!" should read --operatin Col.' 7, line 33, ','operationi should read --operatin Coll. $8, line 37, ".'located" should read -locates.

signed and sealed this 6th day of April 1 971.

(SEAL) Attest: t

EDWARD M.FIETCI-IER,JR. i WILLIAM E. SCHUYLER, JF

Attesting Officer. Commissioner of Patent: 

1. In an ignition system for a two-cycle internal combustion engine having a spark plug and a rotatable part rotated in synchronism with the operation thereof, the combination comprising a trigger coil, means connected with said trigger coil for controlling the firing of said spark plug in response to a trigger signal generated in said trigger coil, a first fluxvArying member carried by said rotatable part for generating a trigger signal in said trigger coil as said rotatable part is rotated, said first flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during forward operation of said engine as to cause firing of said spark plug at such a point in the operation cycle of said engine as to sustain operation of said engine in said forward direction, and a second flux-varying member also carried by said rotatable part for generating a trigger signal in said trigger coil as said rotatable part is rotated, said second flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during reverse operation of said engine that it causes firing of said spark plug at such a point in the operation cycle of said engine as not to sustain said reverse operation.
 2. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by a main generating means for generating power used for firing said spark plug, said main generating means including a part also carried by said rotatable part which carries said first and second flux-varying members.
 3. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 2 further characterized by a condenser connected with said main generating means so as to be charged thereby during each revolution of said rotatable part, means connected with said condenser for producing a spark at said spark plug in response to the discharge of said condenser therethourgh, and an electronic switch device connected between said condenser and said spark-producing means and coupled with said condenser through said spark-producing means in response to the trigger signal produced by said trigger coil.
 4. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by said second flux-varying member being so located on said rotatable part that the trigger signal induced therein is so timed during reverse operation of said engine as to cause firing of said spark plug at a point in the operating cycle of said engine which is more that 40* in advance of the top dead center position of such cycle.
 5. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by said second flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during reverse operation of said engine that it causes firing of said spark plug within the period during which the exhaust valve of said engine is in an open condition.
 6. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by said second flux-varying member being so located on said rotatable part that the trigger signal induced thereby in said trigger coil is so timed during reverse operation of said engine that it causes firing of said spark plug within the period during which the exhaust valve of said engine is in an open condition and the intake valve of said engine is in a closed condition.
 7. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by a trigger stator comprising a permanent magnet and two stator legs on one of which stator legs said trigger coil is mounted, said trigger stator legs extending toward said rotatable part and said first and second flux-varying members being angularly spaced on said rotatable part and arranged to pass said trigger stator in sequence so as to each induce a trigger signal therein during each revolution of said rotatable part.
 8. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 7 further characterized by Said rotatable part being made primarily of a nonmagnetic material and said first and second flux-varying members comprising pieces of magnetic material carried by said rotatable part.
 9. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 8 further characterized by said two pieces of magnetic material comprising said first and second flux-varying members being connected by a thin connecting section of magnetic material integral therewith which accurately angularly located said two members relative to one another, said connecting section being located beyond the zone of said trigger stator.
 10. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 1 further characterized by a condenser, means for charging said condenser once during each revolution of said rotatable part, means connected with said condenser for producing a spark at said spark plug in response to the discharge of said condenser therethrough, an electronic switch device between said condenser and said spark-producing means and coupled with said trigger coil for controlling the timing of the discharge of said condenser through said spark-producing means in accordance with the occurence of the trigger signal produced by said trigger coil.
 11. In an ignition system for a two-cycle internal combustion engine, the combination defined in claim 10 further characterized by a trigger stator located adjacent said rotatable part and carrying said trigger coil, and said two flux-varying members being angularly located on said rotatable part so as to successively pass said stator and induce successive trigger signals in said trigger coil as said rotatable part is rotated. 